1. Field of the Disclosure
This invention relates to lighting systems and more especially although not exclusively it relates to systems for the lighting of film sets or the like.
2. Description of the Related Art
The film making and photographic industries increasingly rely on post production film editing, using sophisticated purpose-built computerized equipment to produce required results quickly and cost effectively, such as for example equipment sold by Quantel Limited under their registered trade marks HARRY, HENRY or DOMINO.
In order to facilitate the use of some post production film making techniques, such as those using blue screen matts for example, whereby a foreground scene may be efficiently superimposed on a background scene filmed at a different location, lighting systems are required which appropriately illuminate both the foreground scene and a blue screen background. The lighting required to illuminate the blue screen background is ideally uniform, soft and shadow free, whereas the lighting required for foreground illumination is usually harder so that shadows are produced which enhance the appearance and character of a subject. It will be appreciated therefore that the lighting requirements for a blue screen background are seldom similar to the lighting requirements for a foreground scene.
Moreover, ideal foreground lighting almost inevitably adversely affects the background due to xe2x80x98hot-spotsxe2x80x99 and/or shadowing, and similarly ideal background lighting usually tends to spill over so as adversely to affect the foreground. Accordingly, known lighting systems for illuminating film sets or the like, tend to be something of a compromise so that neither the blue screen illumination requirements, nor the foreground illumination requirements are fully satisfied.
It is an object of the present invention to provide a lighting system which will efficiently meet at least two different illumination requirements.
According to the present invention, a lighting system comprises a plurality of switchable light generators, light output from which is arranged to be switchble xe2x80x98onxe2x80x99 or xe2x80x98offxe2x80x99, a camera to which light from a scene illuminated by a designated light generator is directed, a scene record inhibitor and sync. signal generator means which is arranged to synchronize switch operation of the light generators with operation of the record inhibitor so that the camera records light from the scene only when the scene is illuminated by the designated light generator.
There may be provided a plurality of cameras at least one of which is arranged to record light from the scene only when the scene is illuminated by the designated light generator.
The lighting system may comprise a beam sharer, by means of which light from a scene is directed along different paths, a plurality of cameras disposed one in each of the paths for receiving light from the scene via the beam sharer, control means operative to ensure that the cameras are arranged to record in turn light originating from the scene via the beam splitter, a plurality of switchable light generators, light output from each of which is arranged to be independently switchable, xe2x80x98onxe2x80x99 or xe2x80x98offxe2x80x99 and sync. signal generator means arranged to synchronize switch operation of the light generators with operation of the control means so that at least one camera records light from the scene only when the scene is illuminated by a designated light generator.
The beam sharer may be a beam splitter such as a part silvered mirror, which splits the beam and feeds it to different paths, or alternatively it may comprise an optical multiplexer such as an oscillating mirror, which feeds the beam alternately to different paths.
According to one embodiment of the present invention, a lighting system comprises a beam splitter, by means of which light from a scene is directed along different paths, a plurality of cameras disposed one in each of the paths for receiving light from the scene via the beam splitter, control means operatively associated with each of the cameras so that the cameras can be arranged to record in turn light originating from the scene via the beam splitter, a plurality of switchable light generators, designated one for each camera, light output from each of which is arranged to be independently switchable, xe2x80x98onxe2x80x99 or xe2x80x98offxe2x80x99 and sync. signal generator means arranged to synchronize switch operation of the light generators with operation of the control means so that each camera records light from the scene only when the scene is illuminated by its designated light generator.
According to one implementation of this embodiment of the invention, the beam splitter is arranged to direct light along two different paths which lead respectively to two cameras each having operatively associated with it control means, two light generators being provided, one being designated for each camera, which are operated alternately and synchronously with the control means so that light originating from one of the two light generators is recorded by one of the two cameras and light originating from the other of the two light generators is recorded by the other of the two cameras.
It will be apparent that with a lighting system according to this implementation of the present invention, light from the said one of the two light generators may be used to provide background illumination for example, whilst light from the said other of the two light generators is used to provide foreground illumination, so that the said one camera receives background light only and the said other camera receives foreground light only. Thus no lighting compromise is necessary since the illumination requirements for background and foreground can both be filly satisfied without adversely affecting each other.
It will be apreciated that in an alternative system one camera might be arranged to operate effectively only when a scene is illuminated by one designated light generator whilst another camera is arranged to operate effectively only when the scene is illuminated by a plurality of light generators, which plurality may include the said one light generator.
The control means may be shutter means operative to interrupt light fed from the beam splitter to the cameras in turn so that they effectively record sequentially.
The shutter may take any convenient form and for example, be a mechanical shutter or an optical shutter of any suitable type, such as for example, an optical shutter comprising rotating polarized elements.
Alternatively, the control means may comprise electronic switch means effective to inhibit operation of the cameras in turn so that they record sequentially.
The cameras may use film which is exposed by received light to record images, or alternatively they may be electronic cameras which use c.c.d. devices or the like to produce electrical image signals.
The light generators may each comprise a light source the energisation of which is controlled by the sync. signal generator means.
Alternatively the light generators may each comprise a light source and a shutter used to occlude light from the source with which it is associated under control of the sync. signal generator means.
A further possible alternative is a combination of switched light source(s) and switched shutter(s) operated under control of the sync. signal generator means.
A shutter used to occlude light from a light source may be a mechanical shutter such as a rotating apertured disc, for example, or alternatively an electronic shutter such as a shutter comprising a liquid crystal obturator.
The shutter means may comprise an occluder placed in the light path such as a mechanical shutter, e.g. a rotating apertured disc, or alternatively it may comprise an electronic shutter such as a shutter comprising a liquid crystal obturator.
Although one implementation of this invention is eminently suitable for providing background illumination and foreground illumination to facilitate the efficient use of blue screen matt processing techniques, it may equally well be used for other purposes, as will hereinafter be described, such as for providing illuminated scene markers for example.
It is also contemplated that three or more different lighting requirements may be provided for, as determined by the particular application in view, whereby for example, illuminated scene markers, background lighting and foreground lighting may each be provided by a light generator, the light generators being operated sequentially so as to avoid any undesirable interference therebetween.